Comparison of wall shear stress estimates obtained by laser Doppler velocimetry, magnetic resonance imaging and numerical simulations

Bauer, Andreas; Wegt, Sebastian; Bopp, Martin; Jakirlić, Suad; Tropea, Cameron; Krafft, Axel J.; Shokina, Nina; Hennig, Jürgen; Teschner, Gabriel; Egger, Herbert

doi:10.1007/s00348-019-2758-6

Cited by 17 publications

(31 citation statements)

References 60 publications

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“…As this work is a continuation of our former investigation (Bauer et al 2019), most experimental procedures and setups remain similar. We will therefore only give a brief description here.…”

Section: Methodsmentioning

confidence: 81%

“…To allow optical accessibility for the LDV measurements, the model has a thin slit, which is covered with a transparent film. The temporal evolution of the flow is the same as in Bauer et al (2019) for exercise conditions (case 3) and shown in Fig. 2.…”

Section: Methodsmentioning

confidence: 99%

“…In addition to the measurements, an analytic solution is available for the inlet, assuming laminar, fully developed pulsating pipe flow (Womersley 1955;Durst et al 1996;Bauer et al 2019).…”

Section: Methodsmentioning

confidence: 99%

“…On the other hand, this work is seen as a continuation of our former work (Bauer et al 2019;Bopp et al 2019), where the goal was to provide ground truth of the underlying WSS of acquired MRV data by comparison measurements and simulations. The MRV data acquired in the present work is intended to also be used as an input and reference for future WSS estimators.…”

Section: Introductionmentioning

confidence: 92%

“…MRV velocity profiles are obtained by circumferential averaging. A detailed description of the procedure can be found in our first publication (Bauer et al 2019). The flow field is divided into 12 equally spaced segments around the circumference, wherein the average velocity profile is calculated.…”

Section: Comparison With Ldv Datamentioning

confidence: 99%

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Analysis of the wall shear stress in a generic aneurysm under pulsating and transitional flow conditions

et al. 2020

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In this study, the flow through a generic abdominal aneurysm under realistic pulsating flow conditions is examined with magnetic resonance velocimetry (MRV), laser Doppler velocimetry (LDV) and computational fluid dynamics (CFD). The influence of flow phenomena on the wall shear stress (WSS) is examined. It is seen that a strong vortex ring develops during systole at the proximal end of the aneurysm and subsequently travels downstream and decays. The vortex formation plays a major role in the temporal and spatial distribution of the WSS, which is analyzed in detail. A peak of the WSS is observed for a very limited time and in a very localized region where the vortex ring initially develops. The intrinsic temporal averaging during the acquisition of the MRV data is found to significantly decrease this peak. CFD and LDV results, which are averaged in the same manner, show a similar behavior. This indicates that besides the spatial resolution, the temporal resolution is a crucial factor, which needs to be considered especially in flows where vortex rings are observed. Results from LDV and CFD show excellent agreement for the velocity field obtained by MRV. While the flow is found to be laminar in the undilated diameter, results show laminar-turbulent transitional behavior for specific phases of the cycle within the aneurysm bulk. Although MRV is not capable of measuring instantaneous velocity fluctuations, we show that the periodic increase in turbulence intensity can be observed from image artifacts in the MRV data. These artifacts increase the velocity uncertainty, which correlates well with the velocity fluctuations measured with LDV. Although the flow encounters laminar and transitional conditions as well as multiple vortices and stagnation and reattachment points, the improved instabilitysensitive Reynolds stress model, which is used for the numerical simulations of this work, shows very good agreement with the measurements. Significant effort has been expended by numerous research groups in recent years in improving the estimation of WSS from MRV data. However, an assessment of these various post-processing methods is only possible if the true values of the WSS are known. The present study is therefore aimed at providing such ground truth WSS values as well as the corresponding MRV data, allowing also other research groups to validate their WSS estimation methods using the experimental data set presented in this work.

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Section: Methodsmentioning

confidence: 81%

Section: Methodsmentioning

confidence: 99%

“…In addition to the measurements, an analytic solution is available for the inlet, assuming laminar, fully developed pulsating pipe flow (Womersley 1955;Durst et al 1996;Bauer et al 2019).…”

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 92%

Section: Comparison With Ldv Datamentioning

confidence: 99%

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Analysis of the wall shear stress in a generic aneurysm under pulsating and transitional flow conditions

et al. 2020

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Toward an accurate estimation of wall shear stress from 4D flow magnetic resonance downstream of a severe stenosis

Corso

Walheim

Dillinger

et al. 2021

Magnetic Resonance in Med

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Purpose First, to investigate the agreement between velocity, velocity gradient, and Reynolds stress obtained from four‐dimensional flow magnetic resonance (4D flow MRI) measurements and direct numerical simulation (DNS). Second, to propose and optimize based on DNS, 2 alternative methods for the accurate estimation of wall shear stress (WSS) when the resolution of the flow measurements is limited. Thirdly, to validate the 2 methods based on 4D flow MRI data. Methods In vitro 4D MRI has been conducted in a realistic rigid stenosed aorta model under a constant flow rate of 12 L/min. A DNS of transitional stenotic flow has been performed using the same geometry and boundary conditions. Results Time‐averaged velocity and Reynolds stresses are in good agreement between in vitro 4D MRI data and DNS (errors between 2% and 8% of the reference downsampled data). WSS estimation based on the 2 proposed methods applied to MRI data provide good agreement with DNS for slice‐averaged values (maximum error is less than 15% of the mean reference WSS for the first method and 25% for the second method). The performance of both models is not strongly sensitive to spatial resolution up to 1.5 mm voxel size. While the performance of model 1 deteriorates appreciably at low signal‐to‐noise ratios, model 2 remains robust. Conclusions The 2 methods for WSS magnitude give an overall better agreement than the standard approach used in the literature based on direct calculation of the velocity gradient close to the wall (relative error of 84%).

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Measurement in opaque flows: a review of measurement techniques for dispersed multiphase flows

Poelma

2020

Acta Mech

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A review is presented of measurement techniques to characterise dispersed multiphase flows, which are not accessible by means of conventional optical techniques. The main issues that limit the accuracy and effectiveness of optical techniques are briefly discussed: cross-talk, a reduced signal-to-noise ratio, and (biased) data drop-out. Extensions to the standard optical techniques include the use of fluorescent tracers, refractive index matching, ballistic imaging, structured illumination, and optical coherence tomography. As the first non-optical technique, a brief discussion of electrical capacitance tomography is given. While truly non-invasive, it suffers from a low resolving power. Ultrasound-based techniques have rapidly evolved from Doppler-based profiling to recent 2D approaches using feature tracking. The latter is also suitable for timeresolved flow studies. Magnetic resonance velocimetry can provide time-averaged velocity fields in 3D for the continuous phase. Finally, X-ray imaging is demonstrated to be an important tool to quantify local gas fractions. While potentially very powerful, the impact of the techniques will depend on the development of acquisition and measurement protocols for fluid mechanics, rather than for clinical imaging. This requires systematic development, aided by careful validation experiments. As theoretical predictions for multiphase flows are sparse, it is important to formulate standardised 'benchmark' flows to enable this validation.

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Comparison of wall shear stress estimates obtained by laser Doppler velocimetry, magnetic resonance imaging and numerical simulations

Cited by 17 publications

References 60 publications

Analysis of the wall shear stress in a generic aneurysm under pulsating and transitional flow conditions

Analysis of the wall shear stress in a generic aneurysm under pulsating and transitional flow conditions

Toward an accurate estimation of wall shear stress from 4D flow magnetic resonance downstream of a severe stenosis

Measurement in opaque flows: a review of measurement techniques for dispersed multiphase flows

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